A data storage device of one type includes a non-volatile memory such as SSDs (solid state drives) and executes a refresh write process to prevent loss of data stored in the non-volatile memory. The refresh write process is a process of writing at least valid data stored in a target block of the non-volatile memory into a different block. Here, the block is a unit of erasing data from the non-volatile memory.
The refresh write process may be executed with priority over other write processes in order to shorten the time required to complete the refresh write process. However, when a request for writing data is received from a host during the refresh write process, a response indicating the write request has completed may be delayed.